In-situ scattering studies of superconducting vacancy-ordered monoclinic TiO thin films

Abstract

We investigate the structural and transport properties of vacancy-ordered monoclinic superconducting $\mathrm{TiO}$ thin films grown by molecular beam epitaxy. The evolution of the crystal structure during growth is monitored by in-situ synchrotron X-ray diffraction. Long-range ordering of Ti and O vacancies in the disordered cubic phase stabilizes the vacancy-ordered monoclinic TiO phase. The reduced structural disorder arising from vacancy-ordering is correlated with a superconductor-metal transition (SMT) in contrast to the superconductor-insulator transition (SIT) observed in cubic TiO, orthorhombic $T{i}_2{O}_3$, and the Magneli $\gamma -T{i}_3{O}_5$ and $\gamma -T{i}_4{O}_7$ phase. Magnetoresistance measurements for the SIT phases indicate superconducting fluctuations persisting in the normal phase. These results confirm the role of disorder related to Ti and O vacancies and structural inhomogeneity in determining the electronic properties of the normal state of titanium oxide-based superconductors.

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